JP2011165843A - Cushioning member for lamination - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cushioning member for lamination capable of uniformly pressurizing recessed materials to be laminated. <P>SOLUTION: In order to solve the problem, the cushioning member 20 includes an internal layer 21, and an upper surface layer 22a and a lower surface layer 22b where the rigidity of the lower surface layer 22b is higher than that of the upper surface layer 22a. Wrinkles or dents can be prevented by using the member when thermocompression-bonding materials to be laminated, and pressure can be uniformly applied. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a cushioning material for lamination used in manufacturing a multilayer printed wiring board formed by bonding and integrating a rigid portion capable of increasing the density of wiring and a wiring substrate having a flexible portion. Is.

  In recent years, as electronic devices have become smaller, thinner, and more advanced, various types of electronic components that make up electronic devices have become smaller and thinner, and multilayer printed wiring boards on which these electronic components are mounted have higher density. Various technological developments that enable mounting are thriving.

  Recently, in multilayer printed wiring boards used in communication terminal devices and other electronic devices, due to space limitations in the electronic devices, some or all of the multilayer printed wiring boards are given flexibility (flexibility). There is a demand for a printed wiring board to be bent and incorporated in an electronic device.

  Conventionally, a multilayer printed wiring board in which a rigid rigid circuit board and a flexible flexible board are integrated has been proposed.

  As shown in FIG. 8, such a multilayer printed wiring board has a rigid circuit board 35 superimposed on both ends of a flexible substrate 34 via an adhesive cover lay 36, The cushion material 33 is overlaid on the surface of the rigid circuit board 35 so as to cover the concave portion 37 formed between them, and is sandwiched between SUS plates and the like, and heated and pressed by a hot press machine to bond the flexible board and the rigid circuit board. By doing so, a multilayer printed wiring board is formed.

  The cushion material 33 is formed by arranging a molding prepreg 32 containing a thermoplastic resin between two release films 31, and filling the recess 37 by melting the thermoplastic resin. Let

  In this state, the flexible board 34, the rigid circuit board 35, and the cover lay 36 with adhesive are heated and pressurized, and the flexible board 34 and the rigid circuit board 35 are bonded by the adhesive action of the cover lay 36 with adhesive. .

  For example, Patent Document 1 is known as prior art document information relating to the invention of this application.

JP-A-7-147484

  However, when used as the cushioning material 33 with the molding prepreg 32 arranged as described above, the flexible substrate 34, the rigid circuit substrate 35, and the cover lay 36 with adhesive are formed due to the recess formed between the rigid circuit substrates 35. And cannot be uniformly pressurized.

  Further, as shown in FIG. 8, when heat and pressure are applied by a press machine, the release film 31 is pulled by the center so that it is pulled by the molding prepreg 32, so that the release film 31 is wrinkled and recessed, and the cover with adhesive There has also been a problem of being transferred to the surface on the ray 36 side.

  The laminate cushioning material of the present invention is used when hot pressing a laminate, and includes an inner layer, an upper surface layer and a lower surface layer laminated on the inner layer, The rigidity of the upper surface layer is larger than the rigidity of the upper surface layer.

  Specifically, this can be realized by making the thickness of the lower surface layer laminated on the inner layer thicker than the thickness of the upper surface layer.

  In addition, the Young's modulus of the lower surface layer material is made larger than the Young's modulus of the upper surface layer material, or the elastic modulus of the lower surface layer material is larger than the elastic modulus of the upper surface layer material. This is also possible.

  By making the rigidity of the lower surface layer, which is a feature of the structure of the present invention, larger than the rigidity of the upper surface layer, gaps with the cushioning material for stacking are formed at the four corners in the recessed portion of the stacked object having the recessed portions. The resin of the cover lay layer with an adhesive can be caused to flow into the recess.

  Accordingly, the bending performance can be improved by reinforcing the boundary portion between the flexible portion and the laminated portion.

  Further, when the cushion material enters the concave portion, which has been a conventional problem, the release film 31 is prevented from being deformed and the release film 31 is transferred to the surface on the cover lay 36 side with the adhesive. This phenomenon can be prevented and the pressure can be uniformly applied.

  By manufacturing a multilayer printed wiring board using the laminate cushioning material of the present invention, the above-mentioned conventional problems are solved, and the conductive insulation between the flexible insulating sheet, the cover lay layer, and the circuit board is excellent and repeated. It is an object of the present invention to provide an excellent multilayer printed wiring board that does not cause conductor cutting or delamination in a multilayer laminated portion even when bent.

Sectional drawing which shows the cushioning material for lamination | stacking in embodiment of this invention Sectional drawing which shows the manufacturing process of the multilayer printed wiring board in the embodiment Sectional drawing which shows the manufacturing process of the multilayer printed wiring board in the embodiment Sectional drawing which shows the manufacturing process of the multilayer printed wiring board in the embodiment Sectional drawing which shows the manufacturing process of the multilayer printed wiring board in the embodiment Sectional drawing which shows the manufacturing process of the multilayer printed wiring board in the embodiment Sectional drawing which shows the manufacturing process of the multilayer printed wiring board in the embodiment Sectional drawing which shows the manufacturing process of the conventional multilayer printed wiring board

(Embodiment)
Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  First, as shown in FIG. 1, the cushioning material 20 for lamination in the thermocompression bonding process described later includes an inner layer 21 containing a thermoplastic resin, an upper surface layer 22a laminated on the inner layer 21, and a lower layer. The rigidity of the lower surface layer 22b is larger than the rigidity of the upper surface layer 22a, and the configuration and the operational effects will be described later.

  Next, the manufacturing process of a multilayer printed wiring board is demonstrated below using FIG.

  FIG. 2A shows a step of preparing a flexible insulating sheet 1 which is divided into a flexible portion F and a laminated portion R, which is commonly called a flexible substrate, and a circuit is formed on the surface layer. b) shows a step of preparing a coverlay layer 2 with an adhesive for insulating coating a flexible insulating sheet, and FIG. 2C shows a circuit as a rigid substrate having a circuit formed on the surface layer. The process for preparing the substrate 3 is shown.

  FIG. 2D shows a thermocompression bonding in which the coverlay layer 2 and the circuit board 3 are laminated on both sides of the flexible insulating sheet 1, and the laminate is thermocompression bonded through the cushioning material for lamination according to the present invention. The process is shown, and the multilayer printed wiring board shown in FIG. 2E is obtained through this process.

  The operation in the manufacturing process of the multilayer printed wiring board of the laminated cushion material of the present invention is shown in the detailed view of the thermocompression bonding process through the SUS board 5 in FIG. 3, and this operation will be described later in “4”. This will be described in “. Configuration of Lamination / Thermo-compression Process”.

1. Configuration of Flexible Insulating Sheet 1 First, the configuration of the flexible insulating sheet 1 having a circuit formed on the surface layer shown in FIG.

  The flexible insulating sheet 1 in the present embodiment is divided into a flexible portion F and a laminated portion R, and a circuit 4 having a thickness of 18 μm is formed on the surface layer.

  The circuit 4 formed on the flexible insulating sheet 1 is formed by etching a copper foil. As the copper foil, an electrolytic copper foil can be used, but by adopting the rolled copper foil, the circuit 4 of the flexible portion F can maintain high bending performance.

  Moreover, the copper foil uses the roughening copper foil of the single side | surface, and after the formation of the circuit 4, after performing the oxidation process, the surface is roughened by giving a reduction process.

  Thereby, the close_contact | adherence with the circuit 4, the flexible insulating sheet 1, and the coverlay layer 2 can be improved.

  The material of the flexible insulating sheet 1 is a polyimide film (DuPont Kapton 100EN / Kapton is a registered trademark of DuPont) having an adhesive layer on the surface.

  Since it is excellent in high-temperature heat resistance, heating and pressurization by hot pressing can be performed in the laminated portion R, and a high multi-layer can be realized.

  In addition, since the adhesive layer is provided, adhesion between the circuit 4 in the flexible portion F and the circuit 4 in the laminated portion R, or the coverlay layer 2 and the circuit board 3 is stabilized, and delamination occurs. It has the effect of preventing.

  Next, a method for manufacturing the flexible insulating sheet 1 will be described.

  FIG. 4 is a cross-sectional view showing the manufacturing process of the multilayer printed wiring board in the embodiment of the present invention, and specifically shows the manufacturing method of the flexible insulating sheet 1.

  First, as shown in FIGS. 4 (a) and 4 (b), a film was applied to the polyimide film 1a having an adhesive layer on the surface as the flexible insulating sheet 1, and an Si-based release agent was applied to one side as an example. A polyethylene terephthalate film 8 (hereinafter referred to as a PET film 8) having a thickness of about 10 μm is laminated, and a through hole 9 is formed in this by laser processing.

  The adhesive layer on the surface of the flexible insulating sheet 1 is preferably composed of an epoxy resin.

  The reason is that by adopting the same material as the epoxy resin constituting the coverlay layer 2 (polyimide sheet 2a), which will be described later, the adhesiveness and peelability to the PET film can be made substantially the same.

  As a result, the conditions for laminating and peeling the PET film can be almost unified, and conductive holes can be formed in the flexible insulating sheet 1 and the coverlay layer 2 using the same production line, thereby improving productivity. Can be made.

  Next, after filling the through-hole 9 with the conductive paste 10a and peeling off the PET film 8, the copper film 11 having a thickness of 18 μm whose one surface on the polyimide film 1a side is roughened is laminated and thermocompression-bonded to form a conduction hole. Both surface layers are electrically connected by 10b {FIGS. 4 (c) to (e)}.

  By using this roughened copper foil, sufficient adhesive force can be obtained while ensuring the electrical connection reliability of the conductive paste.

  Next, as shown in FIG. 4F, the copper foil 11 is selectively removed using a photographic method and an etching method, and the circuit 4 is formed in the laminated portion R and the flexible portion F.

  By the above manufacturing method, the flexible insulating sheet 1 in which the circuit 4 is formed in the flexible portion F and the conduction hole 10b and the circuit 4 are formed in the laminated portion R is obtained. Thereby, the density of the circuit can be increased.

2. Next, the structure of the coverlay layer 2 shown in FIG. 2B will be described.

  The material of the coverlay layer 2 in the present embodiment is a polyimide film having an adhesive layer on the surface in the same manner as the flexible insulating sheet 1 (DuPont Kapton 40EN / “Kapton” is a registered trademark of DuPont). In this configuration, a conductive paste 10a is filled in a through hole provided in the polyimide sheet 2a.

  The manufacturing process is shown in FIG.

  First, as shown in FIGS. 5A and 5B, a PET film 8 is laminated on the polyimide sheet 2a, and a through hole 9 having a diameter of 150 to 200 μm is formed thereon by laser processing. Next, FIG. As shown to c)-(d), the conductive paste 10a is filled into the through-hole 9, and the PET film 8 is peeled off to obtain the coverlay layer 2.

  By using the coverlay layer 2 having the small-diameter conduction holes, the multilayer printed wiring board of the present invention can have high wiring accommodation.

  Note that the circuit 4 of the flexible portion F of the flexible insulating sheet 1 in FIG. 2E is covered with a coverlay layer 2 such as a polyimide material, and the surface of the coverlay layer 2 that contacts the circuit 4 is bonded. A layer is formed, and the opposite surface is subjected to a mold release treatment.

  Thereby, workability | operativity can be improved in the process after a thermocompression bonding process.

3. Configuration of Circuit Board 3 Next, the configuration of the circuit board 3 in which the circuit 4 is formed on the surface layer shown in FIG.

  The manufacturing process is shown in FIG.

  First, a plurality of prepreg sheets 3a used for manufacturing the circuit board 3 are prepared.

  The prepreg sheet 3a has a configuration in which a conductive paste 10a is filled in a through-hole provided in a semi-cured prepreg sheet 3a in which a base material is impregnated with a thermosetting resin.

  The prepreg sheet 3a is a glass woven fabric or nonwoven fabric, or an aramid nonwoven fabric or woven fabric impregnated with an epoxy resin and semi-cured.

  First, as shown in FIGS. 6A and 6B, a PET film 8 is laminated on the prepreg sheet 3a, and a through hole 9 having a diameter of 150 to 200 μm is formed thereon by laser processing. Next, FIG. As shown to c)-(e), the through-hole 9 is filled with the electrically conductive paste 10a, the PET film 8 is peeled, and the prepreg sheet 3b is obtained.

  The circuit board 3 is manufactured by laminating and laminating electrolytic copper foils 11 having a thickness of 18 μm on both sides of the prepreg sheet 3b described above to form a circuit 4 on the surface layer of the copper foil 11 shown in FIG. ), The portion corresponding to the flexible portion F of the flexible insulating sheet 1 is cut and removed in advance using laser processing or a punching die to form a through hole 7.

  Thereby, the multilayer printed wiring board of this invention can make wiring accommodation property high by using the circuit board which has the small diameter conduction | electrical_connection hole 10b.

4). Structure of Lamination / Thermo-compression Process After preparing the flexible insulating sheet 1, the coverlay layer 2, and the circuit board 3 by the above process, as shown in FIG. After the cover flexible layer 2 and the circuit board 3 are laminated on the entire surface of the divided flexible insulating sheet 1 to form a laminate as a laminate having a recess, a laminate cushion is formed on the laminate. The material is sandwiched between stainless plates and hot-pressed with a hot press.

  As shown in FIG. 2D, when the flexible insulating sheet 1, the cover lay layer 2, and the circuit board 3 are laminated, the step between the cover lay layer 2 and the circuit board 3 is the circuit board on both sides in the figure. 3 and a recess 7 surrounded by the coverlay layer 2.

  As shown in FIG. 3, the above-mentioned lamination cushioning material 20 is overlaid on the entire surface of the circuit board 3 so as to cover the opening of the recess 7, and is sandwiched between the SUS plates 5 having a thickness of 2 to 7 mm. Is heated under pressure using a hot press machine or the like.

The pressurizing condition is 40 to 60 kg / cm ² , the heating condition is 3 to 6 ° C./min, the temperature is raised to 170 to 200 ° C., and the temperature is heated for 60 to 90 minutes.

  In the heating process of the heating and pressurizing step, the inner layer 21 and the surface layers 22a and 22b of the cushioning material 20 for laminating increase the fluidity, and follow the pressure injection into the concave portion 7, in particular, the methylpentene copolymer. The surface layers 22a and 22b using the film are in a fluid state at around 60 ° C. and solidify as the temperature rises.

  On the other hand, since the resin of the adhesive layer of the coverlay layer 2 laminated on the laminated portion R of the flexible insulating sheet 1 flows later than the lamination cushioning material 20, it is injected into the recess 7 by pressure and laminated. The cushion material 20 can transmit a uniform pressing pressure to the stack.

  Thereby, the multilayer printed wiring board pressed by the uniform pressure over the whole product surface can be obtained.

  In addition, the cushioning material 20 for lamination | stacking can peel easily, without adhering to a product by having mold release property.

  As shown in FIG. 1, the cushioning material 20 for lamination in the method for manufacturing a multilayer printed wiring board of the present embodiment includes an inner layer 21, an upper surface layer 22a laminated on the inner layer 21, and a lower side layer. And a surface layer 22b.

  The inner layer 21 preferably has a function as an elastic layer and employs a thermoplastic resin sheet mainly composed of ethylene-vinyl acetate copolymer resin (Ethylence-Vinyl Acetate).

  The ethylene-vinyl acetate copolymer resin is more flexible and flexible than a thermoplastic resin such as polyethylene, and has a thermoplastic characteristic that melts when heat is applied, so that it can be reused.

  In addition, it has excellent chemical resistance and colorability, and by using a colored material for the inner layer 21, it can be easily found and removed even when it adheres to a metal plate or the like in the hot press process.

  The inner layer 21 may also be a semi-cured prepreg sheet having a function as an elastic layer obtained by impregnating a glass fiber woven or non-woven reinforcing material with a thermosetting resin.

  Since the prepreg sheet increases fluidity in the temperature raising process of the heating and pressurizing process and follows the pressure injection into the recess 7 and hardens (solidifies) as the temperature rises further, The shape can be stably maintained.

  The surface layers 22a and 22b may be made of silicon rubber or butyl rubber having releasability on the surface layer, more preferably a methylpentene copolymer film (mainly methylpentene copolymer film having a release layer on the surface layer). For example, “TPX” (registered trademark) manufactured by Mitsui Chemicals, Inc. is desirable.

  The methylpentene copolymer film has releasability on the surface layer, and when the laminate reaches about 60 ° C. during heating and heating with a hot press, the methylpentene copolymer film becomes a fluid state at once, and the unevenness and surface of the laminate are This has the property of following the swells so as to be injected under pressure and then solidifying.

  By using the surface layers 22a and 22b having this function, the entire surface of the stack can be more uniformly pressurized.

  The laminated cushioning material 20 is characterized in that the rigidity of the lower surface layer 22b is larger than the rigidity of the upper surface layer 22a, which will be described in detail below.

  First, the thickness of the surface layer is adopted as an element that determines the rigidity of the surface layer.

  That is, in the present embodiment, the thickness of the lower surface layer 22b is desirably larger than the thickness of the upper surface layer 22a.

  Specifically, the surface layer 22a has a thickness of 10 to 30 μm, and the surface layer 22b has a thickness of 90 to 110 μm, and the rigidity of the lower surface layer 22b is larger than the rigidity of the upper surface layer 22a. To do.

  With this configuration, it is possible to provide gaps with the cushioning material for lamination at the four corners of the concave portion of the laminate having the concave portions, and as shown in FIG. The reinforcing portion 6 can be formed by flowing into

  Accordingly, the bending performance can be improved by reinforcing the boundary portion between the flexible portion and the laminated portion.

  Further, when the cushioning material for lamination enters the concave portion, which has been a conventional problem, the lower surface layers 22a and 22b are not twisted and deformed, and can be uniformly pressurized.

  Since the thickness of the surface layers 22a and 22b should not impair the maintenance of strength and cushioning properties, the surface layer 22a has a thickness of 10 to 30 μm, and the surface layer 22b has a thickness of 90 to 110 μm. Thickness is desirable.

  In the above example, the thickness of the surface layer is adopted as an element that determines the rigidity of the surface layer. However, the Young's modulus (longitudinal elastic modulus) of the surface layer material is used as the element that determines the rigidity of the surface layer. Alternatively, the elastic modulus of the surface layer material may be used, and the same effect can be obtained by making the Young's modulus or elastic modulus of the lower surface layer material larger than the Young's modulus or elastic modulus of the upper surface layer material. The effect can be demonstrated.

  As described above, by manufacturing a multilayer printed wiring board using the laminate cushioning material of the present invention, the wiring density is high and the wiring capacity is high, and the conductive insulation between the flexible insulating sheet, the coverlay layer, and the circuit board is reliable. Thus, it is possible to provide an excellent multilayer printed wiring board that is excellent in properties and does not cause conductor cutting or delamination even when it is repeatedly bent.

  From this, it can be said that the industrial applicability of the present invention is great.

DESCRIPTION OF SYMBOLS 1 Flexible insulating sheet 1a Polyimide film 2 Coverlay layer 2a Polyimide sheet 3 Circuit board 3a, 3b Prepreg sheet 4 Circuit 5 SUS board 6 Reinforcement part 7 Through-hole 8 PET film 9 Through-hole 10a Conductive paste 10b Conductive hole 11 Copper Foil 20 Cushion material for lamination 21 Inner layer 22a, 22b Surface layer

Claims (9)

It is used when the laminate is hot pressed,
An inner layer, an upper surface layer and a lower surface layer laminated on the inner layer,
The lamination cushioning material, wherein the rigidity of the lower surface layer is larger than the rigidity of the upper surface layer. The factor that determines the stiffness of the surface layer is the thickness of the surface layer,
The cushioning material for lamination according to claim 1, wherein the thickness of the lower surface layer is larger than the thickness of the upper surface layer. The factor that determines the stiffness of the surface layer is the Young's modulus of the surface layer material,
The cushioning material for lamination according to claim 1, wherein the Young's modulus of the lower surface layer material is larger than the Young's modulus of the upper surface layer. The factor that determines the rigidity of the release film is the elastic modulus of the surface layer material,
2. The lamination cushion material according to claim 1, wherein the elastic modulus of the lower surface layer material is larger than the elastic modulus of the upper surface layer material. The cushioning material for lamination according to claim 1, wherein the surface layer is a methylpentene copolymer film mainly composed of methylpentene having a release layer. The lamination cushion material according to claim 1, wherein the inner layer is an elastic layer using a thermoplastic resin sheet. The lamination cushion material according to claim 1, wherein the inner layer is an elastic layer using a prepreg sheet made of a reinforcing material and a thermosetting resin. The laminated material according to claim 1, wherein the object to be laminated is composed of a laminated body having a recess. The laminated material according to claim 7, wherein the object to be laminated is a multilayer printed wiring board having a flexible portion and a laminated portion.

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